Pressure sensitive adhesive constructions which include a center release liner with pressure sensitive adhesive layers on both sides thereof are known in fiberglass insulation industry and used commercially. Such constructions described in U.S. Pat. Nos. 4,157,410; 4,389,270; and 4,584,217 to McClintock (one of the inventors herein), for example. These patents teach that both pressure sensitive layers are generally the same material, although they may be different, but to the best of our knowledge, have been permanent pressure sensitive adhesives. These patents teach that conventional pressure sensitive type adhesives, viz. the permanent type, may be used, specifically mentioning an adhesive containing an acrylic based or a rubber-based adhesive as well as emulsion adhesive. Also hot melt adhesives may be used. Adhesive constructions manufactured commercially for years under these patents have had permanent pressure sensitive adhesive layers, preferably acrylate, on both sides of the central release liner, and have included exterior release liners typically on both of the pressure sensitive adhesive layers.
These commercial adhesives are of relatively complex construction. Consequently, the industry has attempted for years to go to a simpler construction, viz. less layers or coatings in the sandwich. They have been unable to provide a simpler adhesive construction for insulation of pipe that allowed the insulation to be readily packaged and handled without the adherent surface being protected from being soiled, bent or wrinkled during packaging and handling, which creates installation difficulties and increases the cost and labor.